在c ++中使用std :: for_each进行多态方法

#include<algorithm>
#include<functional>
#include<iostream>
#include<vector>

class Shape {
public:
    virtual double area() const = 0;
};

class Circle : public Shape {
public:
    Circle(double radius) : radius_(radius) {}
    double area() const override { return 3.14159 * radius_ * radius_; }
private:
    double radius_;
};

class Rectangle : public Shape {
public:
    Rectangle(double width, double height) : width_(width), height_(height) {}
    double area() const override { return width_ * height_; }
private:
    double width_;
    double height_;
};

int main() {
    std::vector<Shape*> shapes = {new Circle(5), new Rectangle(3, 4)};

    std::for_each(shapes.begin(), shapes.end(), [](Shape* shape) {
        std::cout << "Area: "<< std::mem_fn(&Shape::area)(shape)<< std::endl;
    });

    return 0;
}